Category: Bad Habits & Best Practices

Discover some undocumented or unsupported behavior you might not even realize you're relying on.

An index of over a decade's worth of posts and videos involving bad habits and best practices in SQL Server.

Originally published in 2009, I updated this in 2019 with an example showing an effect on the plan cache.

Aaron Bertrand explains four conventions he always follows when writing T-SQL queries.

Get a first-hand look at some of the ways NOLOCK can produce incorrect data.

By way of an example, see why most of what you hear about SQL Server is only true some of the time, at best.

See an example that defies a generalization about performance of getting the largest value in a column.

See why it pays to be consistent about always aliasing every table and every column in your query.

IDENTITY columns are very useful, but consider whether they are needed on every single table.

Let's talk about a few of the ways people abuse and misuse DML triggers in SQL Server.

Read about some of the pitfalls of choosing the wrong data type in SQL Server.

In my last post in this series, I talked about using the schema prefix, with particular focus on dbo-only systems.  In this post, I want to treat the use of inconsistent naming conventions. Stored...

In my last post in this series, I talked about inappropriately using SELECT, OUTPUT and RETURN in stored procedures.  Today I wanted to talk about using SELECT * or omitting the column list entirely....

In my last post in this series, I covered the use of "bad" characters in entity names, such as spaces or dashes.  In this post I will talk about using RETURN and OUTPUT inappropriately....

In my last post in this series, I talked about defining varchar columns, parameters, or variables without length.  Next I want to talk about using "bad" characters, like spaces or dashes, in entity names....

In my last post in this series, I talked about using meaningless table aliases.  This time I'm going to talk about a pet peeve of mine: declaring varchar / nvarchar variables or parameters without...

A little wisdom on using sensible and logical aliases for your tables, instead of a / b / c / d.

See a couple of reasons you should stop using old join syntax (FROM t1, t2).

See a few alternatives to expensive loops for populating sample or sequential data.

See why you should always use alias or column names in your ORDER BY clauses, rather than ordinal position.

Read about why you want to use statement terminators throughout all of your T-SQL code.